Switch construction with load break device having one or more movable slats with heat spacers

ABSTRACT

A rotatable switch blade engages and disengages stationary contact assembly through a slot in a generally sector-shaped insulating housing enclosing the contact assembly and formed by either a pair of stationary plates or by a single molded piece of plastic arc extinguishing material. The housing has one or more generally radially extending slats of plastic arc extinguishing material which are located in a groove or grooves on one side of the slot and are biased transversely into a registering groove or grooves on the other side of the slot. The distal end of the switch blade successively engages the outer ends of the slats and displaces them transversely of the slot as the switch blade rotates toward the switch closed position. The reverse procedure occurs when the switch blade rotates toward the switch open position accompanied by arc confining and extinguishing action of the slat or slats and the housing.

United States Patent [72] Inventor James E. Jeffries Chicago, Ill.

[21] Appl. No. 813,541 7 [22] Filed Apr. 4, 1969 [45] Patented May 4, 1971 [73] Assignee S & C Electric Company Chicago, Ill.

[54] SWITCH CONSTRUCTION WITH LOAD BREAK DEVICE HAVING ONE OR MORE MOVABLE SLATS WITH HEAT SPACERS 6 Claims, 23 Drawing Figs.

[52] U.S. C1 200/151,

[51] Int. Cl ..H01h 33/06 [50] Field ofSearch 200/151,

[56] References Cited UNITED STATES PATENTS 2,323,476 7/1943 Lantz, Jr 200/151 2,689,291 9/1954 Christensen... 200/151 3,133,167 5/1964 Miller 200/86X Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attorney-Robert R. Lockwood ABSTRACT: A rotatable switch blade engages and disengages stationary contact assembly through a slot in a generally sector-shaped insulating housing enclosing the contact assembly and formed by either a pair of stationary plates or by a single molded piece of plastic arc extinguishing material. The housing has one or more generally radially extending slats of plastic arc extinguishing material which are located in a groove or grooves on one side of the slot and are biased transversely into a registering groove or grooves on the other side of the slot. The distal end of the switch blade successively engages the outer ends of the slats and displaces them transversely of the slot as the switch blade rotates toward the switch closed position. The reverse procedure occurs when the switch blade rotates toward the switch open position accompanied by are confining and extinguishing action of the slat or slats and the housing.

PATENT-EDMAY 415m v 3576.967 sum 3 OF 7 PATENT EDFAY 4 Ian SHEET 5 (1F 7 comprises a stationary plate of plastic arc extinguishing material secured to the contact assembly and a movable plate of like material that is biased into engagement with the stationary plate. The switch blade in rotating toward closed position moves between the plates and displaces the movable plate. The reverse procedure takes place when the switch blade is rotated toward the switch open position, during which the arc drawn on separation of the switch blade from the stationary contact assembly is confined and extinguished. The efficiency of this device could be improved by decreasing the mass of the movable plate by using movable slats thereby allowing faster closing and restriction of the arc. Also for convenience and reduced cost in moulding the plates, the movable slat approach has merit.

Accordingly, among the objects of this invention are: To reduce the mass of the movable part or parts of a load break device or arc chute on a stationary contact assembly to confine and extinguish the are drawn on separation of a rotatable switch blade from the contact assembly; to employ for this purpose one or more slats of arc extinguishing material mounted for movement transversely of a slot in a housing of arc extinguishing material; to mount each slat in a groove along one side of the slot and to bias it into a registering groove along the other side of the slot; to employ a generally sector-shaped housing with the slat or slats extending generally radially thereof; to arrange for the distal end of the switch blade in closing to engage the outer end of each slat to displace it transversely of the slot as the switch blade rotates toward the switch closed position; to reverse this procedure as the-switch blade is rotated toward the switch open position to confine and extinguish the are drawn on separation of the switch blade from the stationary contact assembly; and to space the switch blade from the slat or slats and from the housing in the switch closed position.

In the drawings: FIG. 1 is a view, in side elevation, of a switch construction provided with a load break device in which this invention is embodied. FIG. 2 is a view, in end elevation looking from left to right, of the arc extinguishing structure shown in FIG. 1. FIG. 3 is a top plan view of the stationary contact assembly and are extinguishing structure shown in FIG. 1. FIG. 4 is a view, in side elevation and at enlarged scale, of the arc extinguishing structure and contact assembly shown in FIG. 1. FIG. 5 is a vertical sectional view taken generally along line 5-5 of FIG. 4. FIG. 6 is a horizontal sectional view taken generally along line 6-6 of FIG. 4.,FIG. 7 is an elevational view of the left housing plate which forms a part of the arc extinguishing structure. FIG. 8 is a view, in end elevation looking from left to right, of the plate shown in FIG. 7. FIG. 9 is a horizontal sectional view taken generally along line 9-9 of FIG. 7. FIG. 10 is an elevational view of the right housing plate which forms a part of the arc extinguishing structure. FIG. 11 is a view, in end elevation looking from right to left, of the plate shown in FIG. 10. FIG. 12 is a horizontal sectional view generally along line 12-12 of FIG. 10. FIG. 13 is an elevational view of the outer arc extinguishing slat. FIG. 14 is a view, in side elevation looking from right to left, of the slat shown in FIG. 13. FIG. 15 is a horizontal sectional view taken generally along line 15-15 of FIG. 14. FIG. 16 is a elevational view of the inner arc extinguishing slat. FIG. 17 is a view, in side elevation looking from right to left, of the slat shown in FIG. 16. FIG. 18 is a horizontal sectional view taken generally along line 18-18 of FIG. 17. FIG. 19 is a view, in side elevation, of a modified form of stationary contact assembly and are extinguishing insulating housing mounted thereon. FIG. 20 is a view, looking from left to right of FIG. 19, certain parts being broken away in order to illustrate the contact structure. FIG. 21 is a horizontal sectional view taken generally along line 21-21 of FIG. 19. FIG. 22 is a sectional view taken generally along line 22-22 of FIG. 19. FIG. 23 is a sectional view taken generally along line 23-23 of FIG. 19.

Referring now to FIG. 1, the reference character 10 designates a switch blade that is mounted on a switch blade support plate 11 which is secured to and is movable with a rotatable insulator 12 that is arranged to be rotated about an axis 13 by an operating arm 14 to which a quick break-quick make operating mechanism is connected for moving the switch blade at high speed to and from the switch closed position. The switch blade support plate 11 has an arcuate extension 15 that is engaged by a sliding contact 16 which extends from a terminal 17 that can be connected to a suitable load such as an industrial or institutional plant, power conducting cable, or the like. The terminal 17 is secured by a bolt 18 to an insulator 19 which is carried by a support plate 20 that forms a part of a support structure for the switch mechanism.

The switch blade 10 is arranged to be rotated into and out of engagement with a stationary contact assembly that is indicated, generally, at 22. The stationary contact assembly 22 is mounted on an insulator 23 which is carried by a support plate 24 that also forms a part of the support structure. A conductor 25 is connected to the stationary contact assembly and is arranged to be connected to a suitable source of power. It will be understood that the conductor 25 and the connection at 17 can be interchanged.

The stationary contact assembly 22, FIGS. 1, 3, 5 and 6, includes opposite hand support brackets 26 and 27 that may be formed of good conducting material such as aluminum. They are provided with flat out-turned sections 28 and 29 having slots 30 therein for receiving bolts 31 to secure the structure to the insulator 23. The support brackets 26 and 27 have rear overlying extensions 32 and 33 and forward-extensions 34 and 35. Mounted on the support brackets 26 and 27 is a bifurcated stationary contact that is indicated, generally, at 36. The stationary contact 36 includes furcations 38 and 39 of resilient good conducting material such as copper alloy. They have end portions 40 and 41 which overlie the rear extensions 32 and 33 of the support brackets 26 and '27 and are secured thereto by bolts 42, FIG. 1. Bolts 43 extend through the assembly for clamping thereto the terminal 44 to which the conductor 25 is connected. The construction is such as to allow the resultant magnetic forces to act to increase contact pressure on flow of short circuit current. In order to hold the furcations 38 and 39 in proper spaced relation a bolt 45, FIG. 6, extends therethrough.

As shown more clearly in FIGS. 5 and 6, the outer ends of the furcations 38 and 39 carry main contacts 46 and 47. They are generally spherical in shape, are secured in position by screws 48 and 49 and are biased toward each other due to the resiliency of the furcations 38 and 39. Auxiliary or arcing contacts 50 and 51 are movable with the main contacts 46 and 47 and are secured by screws 52 and 53 to the upper ends of metallic support arms 54 and 55. The lower ends of the support arms 54 and 55 are secured by rivets 56 and 57 to the furcations 38 and 39. As the switch blade 10 is rotated toward the switch closed position, it first engages the auxiliary or arcing contacts 50 and 51 and thereafter it engages the main contacts 46 and 47. When the switch blade is rotated from the switch closed position, the main contacts 46 and 47 are disengaged while the circuit is completed through the auxiliary or arcing contacts 50 and 51 from which the switch blade 10 separates last and between which any are incident to the opening of the circuit is drawn. The distal end portion 58, FIG. 1, of the switch blade 10 makes contact first with the auxiliary arcing contacts 50 and 51 and disengages them last while the adjacent portion 59 of the switch blade 10 engages and disengages the main contacts 46 and 47 in the manner described.

For the purpose of confining and extinguishing the are that may be drawn between distal end portion 58 of the switch blade 10 and the auxiliary or arcing contacts 50 and 51 when the switch blade 10 is rotated toward the switch open position,

an arc extinguishing structure in the form of an insulating housing of plastic arc extinguishing material is employed, as shown in FIGS. 1, 2 and d. It is indicated, generally, at 60 and is generally sector-shaped and is arranged to be stationarily mounted on the contact assembly 22. A slot 61 is provided in the insulating housing 60 for receiving the switch blade 10 as it is rotated toward or away from the switch closed position. As shown more clearly in the FIG. 2, the entrance edges of the slot 61 are chamfered at 62 and 63 for the purpose of directing the switch blade 10 into the slot 61.' The insulating housing 60 is securely mounted on the contact assembly 22 by bolts 64, FIGS. 1 and 4, which extend through the support brackets 26 and 27.

The insulating housing 60 comprises a left housing plate indicated at 66 and shown in more detail in FIGS. 7, 8 and 9. The insulating housing 60 also comprises a right housing plate that is indicated at 67 and is shown more clearly in FIGS. l0, l1 and 12. Screws 68, FIGS. 2 and 3, extend through the left housing plate 66 and are threaded into the right housing plate 67 for holding them securely together so that the slot 61 of uniform width is provided for receiving the switch blade 10. When the housing plates 66 and 67 are moulded in a one piece construction, as described hereinafter, it is unnecessary to em- I ploy the screws 68.

With a view to confining the are that is drawn on opening of the switch blade 10 and to prevent flashover to an adjacent contact structure or to ground, covers 70 and 71, FIG. 6, extend from the left and right housing plates 66 and 67 over the forward ends of the furcations 38 and 39 and over the main and auxiliary contacts 46-47 and 50-5 1. Screws 72 and 73 of insulating material are employed to hold the covers 70 and 71in position. As shown in FIGS. 9 and 12, the covers 70 and 71 can be moulded integrally with the plates 66 and 67, respectively in which case the screws 72 and 73 are not required. The forward ends 34 and 35 of the support brackets 26 and 27 are enclosed in a cover 76 of suitable insulating material to prevent the are drawn on the opening on switch blade 10 from impinging thereon.

In order to further confine and extinguish the are that is drawn between the distal 58 of the switch blade 10 and the arcing contacts 50 and 51, an arc extinguishing slat 75 of plastic arc extinguishing material is employed. The details of the construction of the slat 75 are shown more clearly in FIGS. 16, 17 and 18. It is arranged to be movably mounted in a groove 76, FIG. 10, that extends generally radially in the right housing plate 67. Coil compression springs 77, FIG. 6, near the upper and lower ends of the slat 75 bias it transversely of the slot 61 and into a registering groove 78, FIG. 7, in the left housing plate 66. Recesses 79 in the rear side of the slat 75 serve to locate the ends of the springs 77. The other ends of the springs 77 are centered on studs 80 which are formed integrally with adjusting screws 81 of plastic insulating material which are threaded into the wall of the right ,housing plate 67.

' If desired to facilitate assembly, the grooves 76 and 78 can be open at their upper ends to receive the slat 75 endwise. By adjusting the screws 81 it is possible to vary the tension of the springs 77 and thereby the forces reacting against the arc extinguishing slat 75 biasing it toward the left housing plate 66. When the required tension of the spring 77 has been determined, springs of that tension are used and the adjusting screws are then omitted.

In order to prevent the flow of arc products through the groove 76 underneath the slat 75, resilient sealing strips 82 are located underneath its opposite sides and between them and the bottom of the groove 76. The sealing strips 82 are formed of expansible foamy material which, in addition, acts to bias the slat 75 toward the left housing plate 66.

Referring to FIGS. 16, 17 and 18, it will be observed that the slat 75 is chamfered at 85 along opposite edges. An inclined striker surface 86 is provided for receiving the distal end 58 of the switch blade 10 and facilitating displacement of the upper end of the slat 75 from the registering groove 78 in the left housing plate 66.

For the purpose of interrupting relatively low load currents at 15 kv. it has been found that the provision of a single arc extinguishing slat 75 is satisfactory. However, when a relatively higher load current up to I200 amperes 60 Hz. is to be interrupted, it has been found desirable to duplicate the slat 75 or to provide another are extinguishing slat 87. The slat 87 is shown in detail in FIGS. l3, l4 and 15 of the drawings and is arranged to be movably mounted in a groove 88 that extends generally radially in the right housing plate 67 that is shown in FIG. 10. The are extinguishing slat 87 is moulded of plastic arc extinguishing material. It is biased for movement transversely of the slot 61 by coil compression springs 89 to a groove 90 in the left housing plate 66 that registers with the groove 88 in the right housing plate 67. It will be observed that the grooves 88 and 90 are open at their upper ends to facilitate entry of the arc extinguishing slat 87 with the left and right housing plates 66 and 67 in assembled relation. The springs 89 are located near the ends of the slat 87 and one end of each of them is located in a recess 91 therein. The other end of each of the springs 89 is centered on a stud 92, FIG. 6, which extends from an insulating adjusting screw 93. The tension of the springs 89 can be adjusted by the screws 93. The slat 87 is chamfered as indicated at 95 along its edges and is provided with an inclined striker surface 96 near its upper end for receiving the distal end 58 of the switch blade 10 to facilitate displacing of the slat 87 as the switch blade 10 is rotated toward the switch closed position.

In order to absorb some of the shock incident to stopping rotation of the switch blade 10 when the main contacts 46 and 47 are engaged by the portion 59 of the switch blade 10, a resilient bumper 99, FIG. 5, formed of suitable resilient material is located above the support brackets 26 and 27 on the forward extensions 34 and 35 thereof.

In the event that fault current of the order of l0,000 amperes or more flows through the switch blade 10 in the switch closed position, it is heated to a relatively high temperature. Accordingly, it is desirable to space it from the insulating housing 60 and from the slats 75 and 87 to a slight extent since they are formed of material which would be adversely affected by the heat incident to such current flow. For this purpose, a

pair of heat resistance spacers 100, FIGS. 4, 7, and 8 is provided on the left housing plate 66 to engage one side of the switch blade 10 in the switch closed position. Heat resistant spacers 101 and 102, FIGS. 13 to 18, are provided on the slats 75 and 87 near their lower ends for engaging the other side of the switch blade-l0. In the switch closed position the switch blade 10 is engaged on opposite sides only by the heat resistant spacers 100, I01, and 102.

In operation, when the switch blade 10 is in the open position shown in FIG. 1, the arc extinguishing slats 75 and 87 are biased transversely of the slot 61 into the registering grooves 78 and 90 of the left housing plate 66. As the switch blade 10 is rotated in a clockwise direction toward the switch closed position, the distal end 58 engages the striker surface 96 on the outer end of slat 87 and displaces this end transversely of the slot 61 against the biasing action of the upper coil compression spring 89. The lower end of the slat 87 is then displaced only a slight extent. As the switch blade 10 continues to be rotated toward the switch closed position, its intermediate portion moves along the juxtaposed surface of the slat 87 and shifts it from the groove 90 into the groove 88. As the rotation of the switch blade 10 continues, the upper end of the slat 87 is restored to its original position while the lower end is displaced from the lower end of the groove 90 into the lower end of the groove 76. At the same time, as the distal end 56 of the switch blade 10 engages the inclined striker surface 86 of the slat 75, its upper end is displaced transversely from the groove 78 in the left housing plate 66 across the slot 61 and into the upper end of the groove 76 in the right housing plate 67. The continued rotation of the switch blade 10 toward the switch closed position is accompanied by the downward sweep of the switch blade 10 along the slat 75 to displace it from the upper end toward the lower end into the groove 76 in the right housingplate' 67. The circuit is completed when the distal end 58 engages the auxiliary or arcing contacts 50 and 51 and spreads them apart from the position shown in FIG. 5. The continued rotation of the switch blade in the clockwise direction brings the portion 59 of the switch blade 10 into contact engagement with the main contacts 46 and 47 which are spread apart. They are held in good contact engagement with the por tion 59 of the switch blade 10 by the resiliency of the furcations 38 and 39. In the switch closed position, the opposite sides of the switch blade 10 are engaged by the heat resistant spacers 100, 101 and 102, as described, to maintain a slight spacing between it and the adjacent walls of the housing plates 66 and 67 and of the lower ends of the slats 75 and 87.

When the switch is opened, the switch blade 10 is rotated in a counterclockwise direction to shift the portion 59 of the switch blade 10 out of engagement with the main contacts 46 and 47 and to' transfer the current flow to the auxiliary contacts 50 and 51 on engagement thereby with the distal end 58. As'the rotation in the opening direction of the switch blade 10 continues, its distal end 58 separates from the arcing contacts 50 and 51 and an arc is drawn therebetween. The are is confined by the covers 70 and 71 and between the walls of the slot 61 in the insulating housing 60. The are is further confined by the slat 75 and by the slat 87, if it is used. As the switch blade 10 rotates in the switch opening direction, it moves upwardly along the slat 75 which is displaced from its lower end to its upper end under the biasing action of the springs 77 and the retreating movement of the switch blade 10. Because of the relatively small mass of the slat 75, the slot 61 is rapidly closed. Due to the arc extinguishing gas that is evolved from the surface of the slat 75 and the surfaces of the housing plates 66 and 67 between which the slot 61 is formed, the arc is rapidly extinguished. As the switch blade 10 continues to rotate toward the open position, the slats 75 and 87 are restored from their lower ends to their upper ends into the grooves 78 and 90 in the left housing plate 66 to effectively close off the slot 61. As the switch blade 10 is rotated toward the open position, the lower ends of the slats 75 and 87 begin to move across the slot 61 and thereby begin to close off this area to prevent discharge of the are products into the area along the undersides of the plates 66 and 67.

Since the left and right housing plates 66 and 67 are rigidly secured to the stationary contact assembly 22, a satisfactory mechanical construction is provided. Only the relatively small mass slats 75 and 87 are movable and they are positively confined within their respective grooves 76 and 78 and 88 and 90. Thus the arc extinguishing structure 60 can be readily and economically assembled and installed.

In FIGS. 19 to 23 there is disclosed a modified form of the present invention. It includes a stationary contact assembly that is indicated, generally, at 109 which is arranged to be mounted on insulator 23 for cooperation with the switch blade 10 as shown in FIG. 1 and to be connected to the conductor 25. The stationary contact assembly 109 includes metallic support brackets 110 and 111. They have out-tumed flat sections 112 and 113 for mounting on the insulator 23 in the manner previously described. The support brackets 110 and 111 also include rear extensions 114 and 115 and forward extensions 116 and 117. A bifurcated stationary contact, indicated generally at 118, is mounted on the support brackets 110 and 111. The stationary contact 118 includes flat rear sections 120 and 121 which overlie the rear extensions 114 and 115 and are secured thereto by bolts 122. Extending forwardly and outwardly from the flat rear sections 120 and 121 are upper furcations 124 and 125 and lower furcations 126 and 127. Main contacts 128 and 129 are secured by screws 128 and 129' to the forward ends of the lower furcations 126 and 127. The main contacts 128 and 129 are arranged to be engaged by the portion 59 of the switch blade 10 in the switch closed position that is adjacent to the distal end portion 58. Auxiliary or arcing contacts 130 and 131 are secured by screws 130' and 131' to the forward ends of the upper furcations 124 and 125. They are arranged to be engaged by the distal end portion 58 of the switch blade 10 prior to engagement with the-main contacts 128 and 129 and to be disengaged last when the switch blade 10 is swung to the open position. The upper furcations 124 and and the lower furcations 126 and 127 are held in spaced apart relation by contact adjustment bolts 132. Their resiliency is such that, when the switch blade 10 is swung between the auxiliary or arcing contacts and 131 and between the main contacts 128 and 129, these contacts are spread apart to provide contact engagement under substantial pressure with the opposite sides of the switch blade 10.

An insulating cover 133 overlies the ends of the forward extensions 116 and 117 to avoid impingement of an arc thereon during the closing or opening movement of the switch blade 10. A guide pin 134 extends through theforward extensions 116 and 117 and through the cover 133 to hold it in position.

An arc extinguishing structure in the form of a one piece sector-shaped insulating housing, indicated generally at 137, is mounted on the contact assembly 139 and is secured thereto by bolts 138 that are formed of insulating material. The housing 137 is formed by moulding a suitable plastic arc extinguishing material. The bolts 138 extend through opposite sides of the insulating housing 137 and through the forward extensions 116 and 117 of the support brackets 110 and 111. Instead of forming the arc extinguishing structure of a pair of housing plates, such as the housing plates 66 and 67 previously described, the insulating housing 137, as pointed out is moulded principally in one piece and a slot 139 is formed therein between a left wall 140 and a right wall 141 for receiving the switch blade 10 for engaging and disengaging the stationary contact assembly 109. The left and right walls 140 and 141 are joined integrally by a bottom wall 142 and by connecting wall sections 143 and 144 along the upper right side as shown in FIG. 19.

For arresting closing movement of the switch blade '10 there is provided an impact pad 146, FIG. 21, along a portion of the bottom of the slot 139 and underneath the main contacts 128 and 129.

In order to enclose the left end of the bifurcated stationary contact 118, extensions 147 and 148 are moulded integrally with the left and right walls 140 and 141 respectively. The extensions 147 and 148 overlie the upper furcations 124 and 125 and the lower furcations 126 and 127 for a substantial extent and thereby minimize the likelihood of an are striking over the exterior surface of the insulating housing 137, particularly when the switch blade 10 is swung to the open position.

For closing off the slot 139 as the switch blade 10 is swung to the open position and confining any arc drawn in the vicinity of the auxiliary or arcing contacts 130 and 131, a radially extending arc extinguishing slat 149 is loosely located within a radially extending groove 150 in the right wall 141. The slat 149 is biased across the slot 139 by a flat spring 151 into a complementary groove 152 that is moulded in the left wall 140. As shown in FIG. 21 the cross section of the slat 149 is generally C-shaped and the edge portions 153 are slidably mounted in narrow slots 154 that are. moulded in the right wall 141. By providing the edge portions 153 along the slat 149 and extending them into the narrow slots 154 an effective seal is provided against the flow of are products along the slat 149 on the side adjacent the right wall 141. This construction permits the slat 149 to be displaced as the switch blade 10 moves toward the switch closed position and to close off the slot 139 as it moves toward the open position. The leading edge engaged by the switch blade is chamfered at 155 and a striker surface 156, FIG. 19, is moulded into the slat 149 near its upper end to facilitate initial displacement of the slat 149 on engagement by the distal end 58 of the switch blade 10. The upper ends of the grooves 150 and 152 are open in order to permit assembly of the slat 149 and flat spring 151 therein. After the slat 149 and flat spring 151 have been inserted, the upper ends of the grooves 150 and 152 are closed by an insulating closure plate 157 that is held in place by an insulating screw 158.

For the reasons outlined hereinbefore it is desirable to space the switch blade 10 in the switch closed position from the adjacent portions of the insulating housing 137 and the slat 149. For this purpose a circular heat resistant spacer 161, FIG. 21, is inserted in the slat 149 near its lower end. The spacer 161 projects a slight distance from the adjacent surface of the slat 149 and engages the juxtaposed side of the switch blade 10. A shallow opening 162 in the left wall 140 is arranged to receive the heat resistant spacer 161 when the switch blade 10 is withdrawn. The shallow opening 162 is located in an elongated dovetail insert 163 of heat resistant material which is positioned in a dovetail slot 164 that is moulded in the left wall 140. The insert 163 is placed in operative position in the slot 164 prior to mounting of the insulating housing 137 on the stationary contact assembly 109. It is held in place by a bump 165 which extends a slight distance into an opening 166 to the left wall 140. In order to space the opposite side of the switch blade 10 from the insert 163 throughout its major extent a bump 167 is formed thereon.

With a view to providing for further confining the are that is drawn between the retreating switch blade 10 and the auxiliary arcing contacts 130 and 131, a second radially arc extinguishing slat 171 is employed. As shown, it is located outwardly of the slat 149 and is arranged to be engaged first and disengaged last by the switch blade 10 in its movement toward the closed and open positions. The are extinguishing slat 171 is loosely positioned within a groove 172 that is moulded into the right wall 141 and it is biased by a flat spring 173 across the slot 139 into a groove 174 that is formed in the left wall 140. The leading edge of the slat 171 is chamfered at 175 and a striker surface 176, FIG. 19, is moulded into the slat 171 near its upper end for receiving the distal end 58 of the switch blade 10 during its movement toward the closed position. The upper ends of the grooves 172 and 174 are open to permit insertion of the slat 171 and the flat spring 173. Their upper ends are closed by an insulating closure plate 177 which is held in place by a screw 178 of insulating material. Near its lower end the slat 171 carries a heat resistant spacer 181 which serves to engage the juxtaposed side of the switch blade 10 in the switch closed position for holding it in spaced relation to the slat 171. In the absence of the switch blade 10, the heat resistant spacer 181 moves into a shallow opening 182 in the elongated dovetail insert 163. Thus the switch blade 10 in the switch closed position is held in spaced relation to the juxtaposed surfaces by the spacers 161 and 181 on one side and by the bump 167 on the elongated dovetail insert 163 on the opposite side.

The operation of the insulating housing 137 in conjunction with the movable slats 149 and 171 is essentially the same as previously described for the insulating housing 60 and the movable slats 75 and 87.

Iclaim:

1. A circuit interrupter comprisingiterminals for connecting said interrupter in a circuit,

contact means mounted on one of said terminals,

a switch blade movably mounted on the other of said terminals,

an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out ofengagement with said contact means,

an arc extinguishing slat movable within said housing transversely of said slot,

means biasing said slat toward a position closing off said slot,

said slat being arranged to be engaged initially near one end by the distal end of said switch blade in moving to closed position and to be engaged longitudinally and transversely thereby as said switch blade moves toward the other end of said slat into engagement with said contact means and to be reversely engaged as said switch blade moves away from said contact means, and

heat resistant spacer means on said housing and on said slat for engaging said switch blade in the switch closed position and spacing said switch blade from said housing and said slat.

2. The circuit interrupter according to claim 1 wherein a second arc extinguishing slat is movable within said housing transversely of said slot and is arranged to be engaged by said switch blade during its movement toward switch closed position in the same manner as and before said switch blade engages the first mentioned arc extinguishing slat and to be disengaged last by said switch blade during its movement toward switch open position in the same manner as said first mentioned slat is disengaged by said switch blade, and

heat resistant spacer means on said housing and on said slats engage said switch blade in switch closed position and space said switch blade from said housing and said slats.

3. The circuit interrupter according to claim 1 wherein said heat resistant spacer means on said housing is carried by an elongated insert interfitting with a wall of said housing.

4. The circuit interrupter according to claim 2 wherein said heat resistant spacer means on said housing is carried by an elongated insert interfitting with a wall of said housing.

5. A circuit interrupter comprising:

terminals for connecting said interrupter in a circuit,

contact means mounted on one of said terminals,

a switch blade rotatably mounted on the other of said terminals,

a generally sector-shaped insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means,

said housing including a pair of plates between which said slot is located and one of said plates having a slat receiving groove extending generally radially thereof, partially therethrough from said slot, between said contact means and said switch blade in the switch open position, and transversely of said switch blade in switch closed position,

a flat arc extinguishing slat having a relatively large surface area movable in said groove transversely of said slot toward and away from the other of said plates, and with said housing blocking off the space between said contact means and said switch blade in the switch open position to prevent flow of are products into said space, and

means biasing said slat in said groove toward the other of said plates to a position closing off said slot,

said slat being arranged to be engaged initially near one end by the distal end of said switch blade in moving to closed position and to be engaged longitudinally and transversely thereby as said switch blade moves toward the other end of said slat into engagement with said contact means and to be reversely engaged as said switch blade moves away from said contact means for extending, restricting and confining an are drawn between said switch blade and said contact means in the direction of blade opening movement along said slat whereupon said space is closed off beginning adjacent said contact means by said slat being moved by said biasing means out of said groove toward said other plate and continuing until said one end of said slat is disengaged by said distal end of said switch blade.

6. The circuit interrupter according to claim 5 wherein:

said one plate has a second slat receiving groove extending generally radially thereof and only partially therethrough from said slot,

21 second 'flat arc extinguishing slat having a relatively large surface area is movable in said second groove transversely of said slot toward and away from the other of said plates and is arranged to be engaged by said switch blade during its movement toward switch closed position in the same manner as and before said switch blade engages the first mentioned are extinguishing slat and to be disengaged last by said switch blade during its movement toward switch open position in the same manner as said first mentioned slat is disengaged by said switch blade for extending, restricting and confining said are, and

means bias said second slat toward the other of said plates to a position also closing off said slot. 

1. A circuit interrupter comprising: terminals for connecting said interrupter in a circuit, contact means mounted on one of said terminals, a switch blade movably mounted on the other of said terminals, an insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, an arc extinguishing slat movable within said housing transversely of said slot, means biasing said slat toward a position closing off said slot, said slat being arranged to be engaged initially near one end by the distal end of said switch blade in moving to closed position and to be engaged longitudinally and transversely thereby as said switch blade moves toward the other end of said slat into engagement with said contact means and to be reversely engaged as said switch blade moves away from said contact means, and heat resistant spacer means on said housing and on said slat for engaging said switch blade in the switch closed position and spacing said switch blade from said housing and said slat.
 2. The circuit interruptEr according to claim 1 wherein a second arc extinguishing slat is movable within said housing transversely of said slot and is arranged to be engaged by said switch blade during its movement toward switch closed position in the same manner as and before said switch blade engages the first mentioned arc extinguishing slat and to be disengaged last by said switch blade during its movement toward switch open position in the same manner as said first mentioned slat is disengaged by said switch blade, and heat resistant spacer means on said housing and on said slats engage said switch blade in switch closed position and space said switch blade from said housing and said slats.
 3. The circuit interrupter according to claim 1 wherein said heat resistant spacer means on said housing is carried by an elongated insert interfitting with a wall of said housing.
 4. The circuit interrupter according to claim 2 wherein said heat resistant spacer means on said housing is carried by an elongated insert interfitting with a wall of said housing.
 5. A circuit interrupter comprising: terminals for connecting said interrupter in a circuit, contact means mounted on one of said terminals, a switch blade rotatably mounted on the other of said terminals, a generally sector-shaped insulating housing enclosing said contact means and having a slot through which said switch blade is movable into and out of engagement with said contact means, said housing including a pair of plates between which said slot is located and one of said plates having a slat receiving groove extending generally radially thereof, partially therethrough from said slot, between said contact means and said switch blade in the switch open position, and transversely of said switch blade in switch closed position, a flat arc extinguishing slat having a relatively large surface area movable in said groove transversely of said slot toward and away from the other of said plates, and with said housing blocking off the space between said contact means and said switch blade in the switch open position to prevent flow of arc products into said space, and means biasing said slat in said groove toward the other of said plates to a position closing off said slot, said slat being arranged to be engaged initially near one end by the distal end of said switch blade in moving to closed position and to be engaged longitudinally and transversely thereby as said switch blade moves toward the other end of said slat into engagement with said contact means and to be reversely engaged as said switch blade moves away from said contact means for extending, restricting and confining an arc drawn between said switch blade and said contact means in the direction of blade opening movement along said slat whereupon said space is closed off beginning adjacent said contact means by said slat being moved by said biasing means out of said groove toward said other plate and continuing until said one end of said slat is disengaged by said distal end of said switch blade.
 6. The circuit interrupter according to claim 5 wherein: said one plate has a second slat receiving groove extending generally radially thereof and only partially therethrough from said slot, a second flat arc extinguishing slat having a relatively large surface area is movable in said second groove transversely of said slot toward and away from the other of said plates and is arranged to be engaged by said switch blade during its movement toward switch closed position in the same manner as and before said switch blade engages the first mentioned arc extinguishing slat and to be disengaged last by said switch blade during its movement toward switch open position in the same manner as said first mentioned slat is disengaged by said switch blade for extending, restricting and confining said arc, and means bias said second slat toward the other of said plates to a position also closing off said slot. 